Early every spring, the Storm Prediction Center releases final data for the year prior.
This year seemed like a good time to cook up tornado average maps for annual numbers, and every month individually, so we could have our own here on the site. I’ve followed the general methodology from the Storm Prediction Center, which currently has averages updated through 2013 using a 25-year period.
Details here are minimal, basically just the hard facts, given we already have a post that breaks down a lot of these ideas by state and region (that post may need some updating soon!).
An average of 1,224 tornadoes touch down per year across the United States.
While the southern into central Plains represents strongly, much of the South and Midwest ranks up there nearly as high as the states most frequented by tornadoes.
Jump to month: January | February | March | April | May | June | July | August | September | October | November | December
Of the 1,224 twisters in your average year, 36 tornadoes touch down in January.
32 tornadoes occur in February, that’s actually a slight downturn since January but basically a head-to-head match up.
The onset of the spring season is often apparent by now, at least in fits and starts. 75 tornadoes scour the landscape during March in an average year, with a majority striking the South, the Midwest and the Plains.
As peak tornado season gets underway, April can still be hit-or-miss. 178 tornadoes touch down in April which puts it well ahead most months. And, of course, there are many memorable April events.
“When it’s May you chase,” and hope these frequent beasts manage to miss population. 269 tornadoes occur in an average May, the highest tally of the year, and continually backing northwest into better storm chasing terrain across the Plains.
At least the second best month for storm chasing. 229 tornadoes touch down in June as the final month of peak tends to target the high Plains, the northern Plains, and the Midwest. This can be an active Chicago to East Coast month as well.
Tornado “patterns” begin to lose coherency in July but the migration north and west generally persists. 123 tornadoes happen in July on average, the fourth highest of any month. This is another month which tends to target the northeast U.S.
August is kind of like a deflated July. There are often tornadoes all over the place, just not many in one spot. 75 tornadoes touch down in August on average, which makes it the March of late summer.
September features 66 tornadoes on average, usually continuing the August deflation. It also shows the beginning of a southward constriction back toward the Gulf warmth headed to winter. There’s also a tendency for tropical influence in the South and mid-Atlantic.
Tornadoes continue to wane into October, but much of the nation has still been impacted during the month. There are 58 tornadoes in October on average, and the Plains into the South become a favored zone once again.
November, like October, can be part of “second season” in many years. It’s usually nothing like the first season and doesn’t always occur. Although the average count drops to 56 tornadoes across the country in November, numbers go up across the south from October.
This is not a month to sleep on, as 2015 sadly reminded us. However, it’s the low point of the tornado year right now, 27 tornadoes occurr in December on average.
The tornado year features four months with over 100 tornadoes on average, running April through July. While the typical tornado season is often thought of as the peak months of April through June, most months have featured significant tornado events at one time or another.
By meteorological season, roughly 8 percent of tornadoes occur during winter, 43 percent in spring, 35 percent in summer, and 15 percent in fall.
Notes…
Averages were produced using Storm Prediction Center data run through GIS.
State values added will not equal the monthly average exactly because some tornadoes cross state lines and are counted for each state impacted. The monthly and annual values are averages of the 25 year sample combined without splitting by state.
Color shades correspond to rounded values.
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Not being a memorized expert on the state outlines of the USA, the state symbol should be included for easiest data digestion to geographic
illiterates such as myself. I was particularly interested in tornados as they happen along the TransAm bicycle route which crosses through Colorado and Kansas and I plan to ride through there starting at the Kansas state line on April 01, 2017. But your site is useful and I appreciate it !
Same! Going Portland, ME to Portland, OR via TransAm bike route, hitting Kansas end of May to early June. Should tornadoes be a concern and/or should I look at rerouting further north? Not really much chance of out-pacing a tornado...
Wow I always thought the summer was the low point! Thank you for this it was interesting
what i read about it basicly about tornadoes and how to make a plan to me thats what i think it is about